feat: Implement EventSource

docs/api/EventSource.md

@@ -0,0 +1,21 @@
+# EventSource
+
+Undici exposes a WHATWG spec-compliant implementation of [EventSource](https://developer.mozilla.org/en-US/docs/Web/API/EventSource)
+for [Server-Sent Events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events).
+
+## Instantiating EventSource
+
+Undici exports a EventSource class. You can instantiate the EventSource as
+follows:
+
+```mjs
+import { EventSource } from 'undici'
+
+const evenSource = new EventSource('http://localhost:3000')
+evenSource.onmessage = (event) => {
+  console.log(event.data)
+}
+```
+
+More information about the EventSource API can be found on
+[MDN](https://developer.mozilla.org/en-US/docs/Web/API/EventSource).

docsify/sidebar.md

@@ -10,6 +10,7 @@
   * [ProxyAgent](/docs/api/ProxyAgent.md "Undici API - ProxyAgent")
   * [Connector](/docs/api/Connector.md "Custom connector")
   * [Errors](/docs/api/Errors.md "Undici API - Errors")
+  * [EventSource](/docs/api/EventSource.md "Undici API - EventSource")
   * [Fetch](/docs/api/Fetch.md "Undici API - Fetch")
   * [Cookies](/docs/api/Cookies.md "Undici API - Cookies")
   * [MockClient](/docs/api/MockClient.md "Undici API - MockClient")

examples/eventsource.js

@@ -0,0 +1,20 @@
+'use strict'
+
+const { randomBytes } = require('crypto')
+const { EventSource } = require('../')
+
+async function main () {
+  const url = `https://smee.io/${randomBytes(8).toString('base64url')}`
+  console.log(`Connecting to event source server ${url}`)
+  const ev = new EventSource(url)
+  ev.onmessage = console.log
+  ev.onerror = console.log
+  ev.onopen = console.log
+
+  // Special event of smee.io
+  ev.addEventListener('ready', console.log)
+
+  // Ping event is sent every 30 seconds by smee.io
+  ev.addEventListener('ping', console.log)
+}
+main()

index.js

@@ -149,3 +149,7 @@ module.exports.MockClient = MockClient
 module.exports.MockPool = MockPool
 module.exports.MockAgent = MockAgent
 module.exports.mockErrors = mockErrors
+
+const { EventSource } = require('./lib/eventsource/eventsource')
+
+module.exports.EventSource = EventSource